1. Field of the Invention
The present invention relates to the field of building construction and, in particular, to a modular system for assembling school buildings.
2. Description of the Related Art
School construction has typically proceeded in a manner very similar to that of traditional residential home construction. An architect first drafts a set of plans for the building. The plans are then checked and approved by the client and the responsible regulatory agency. The design, drafting, and approval process typically takes a year or so, particularly as changes are often required by the client or the approval entity. Once the plans are approved, the actual construction of the building takes place, commencing typically with preparing the building site by clearing and leveling the land. The foundation is then prepared, the frame of the building is erected, covering material is applied to the interior and exterior of the building, and the interior flooring and windows and door are installed. Plumbing and electrical wiring are also installed along with increasingly common telephone and high-speed communication lines.
While ground up construction offers the advantage that a school can be thereby designed and built specifically for the requirements of a particular building location and client, this specificity incurs significant costs in architect's and approval fees and time. The typical duration for building a traditional permanent school is four years from inception to completion. With the rapidly changing populations, particularly of school age children, that many portions of the country are experiencing, a four year lag time from request to build a new school building until it is ready for use imposes a significant burden to the schools and the children using them.
As an alternative to site assembled permanent structures, partially premanufactured school buildings are sometimes used. The portable buildings may be single structures, similar to mobile homes, or more typically, consist of two structures, each enclosed on three sides with one open wall that are joined together at the open walls to form single structures. The partially preassembled buildings, typically referred to as “portables”, are placed on a foundation pad. Plumbing, electrical wiring, telephone lines, and heating, ventilation and air conditioning (HVAC) systems are installed. Portables are available in standard sizes and typically come with insulation, exterior wall finishing, and roofs already included.
In order to be portable, the structure and materials of the portable buildings are typically lightweight and the size of the structure is such as to fit under overpasses and bridges over roads. While convenient, the lightweight construction and size of portables presents several drawbacks to their use as school buildings. They generally employ a limited amount of insulation in the walls and roof and are often placed directly on a wood foundation. Thus, the insulative capabilities of a portable are generally lower and the associated heating and cooling costs are generally higher than for a better-insulated permanent building of comparable size. In addition, the light structure and the typical manner of joining the two separate sections of typical portables makes the portable buildings not as structurally durable over time. They tend to develop creaky floors and windows and doorframes that distort and make the opening and closing of the windows and doors problematic. The joint between the two sections of the portable is a potential source of drafts, dirt, and pests and also structural flexing.
The requirement for a portable to fit under overpasses and bridges means that, in practice, the overall height of a typical portable is limited to approximately 12 feet. The ceilings and corresponding roofs are also typically flat in order to simplify construction. The footprint of a portable building is typically constrained by the standard sizes of portables available. With a limited footprint and a ceiling that is typically no more than 9 feet high, the interior volume of a portable building is limited. This can become a concern, because a school classroom building often contains 30 or more children and adults all of who require clean air to breathe and who generate carbon dioxide as they exhale. Excessive concentration or accumulation of carbon dioxide, dust, pollen, particulates, or noxious vapors are a known health hazard, particularly around children. The limited volume of air per person of a portable building places significant demands on the building's HVAC system to provide fresh air to the inhabitants.
Another disadvantage of typical portables is the flat roof profile itself. The lack of a pitch to the roof profile allows a significant amount of snow, rainwater, dirt, and debris to accumulate on the rooftop. This imposes a significant weight load on the roof. In areas with significant snowfall, the use of buildings with flat roofs is often precluded. In addition, accumulated water and debris can attack the roofing materials leading to leaks in the roof appearing prematurely.
Also, since the roof is generally multi-layered, a leak in the outer layer will allow water to ingress, however the water may migrate laterally within the layers of a flat roof so that a water leak into the interior of the building is not necessarily immediately below the external break in the roofing material. This makes locating a leak source and repairing it more difficult.
The flat roof of a typical portable is typically separated from the interior ceiling by rafter structures and insulation material with a thickness on the order of 1 foot. The outer roof of the portable is exposed to thermal heating from the sun and cooling from exposure to the ambient air. It can be appreciated that the thermal insulation factor of a portable with a flat roof surface in relative proximity to the interior ceiling is inferior in comparison to that of a permanent structure with a pitched roof profile and an enclosed dead air space between the roof surface and the interior ceiling surface, assuming comparable insulation materials in the two structures. In practice, a permanent structure with an upper roof displaced from the ceiling provides additional space for dedicated insulation material in comparison to a portable with the upper roof and the ceiling positioned adjacent each other.
Many portable building designs lack provision for securely fastening the building to the foundation. A secure attachment is required to inhibit uplift of the building from the foundation in case of a seismic event or high wind conditions. The anchoring methods utilized by many portable designs incorporates metal strapping or anchors shot into the foundation that are typically not strong enough to inhibit building uplift in an extreme stress event.
It can be appreciated that there is an ongoing need for a system to provide permanent, structurally sound school buildings in a reduced time frame. The system should provide a pitched roofline to facilitate shedding rain, snow, and debris and increased interior volume for a given floor area. However, the system should also be configured to be able to be transported over the road from the manufacturing facility to the building site in a substantially preassembled condition to reduce the time of construction. The system should provide a manner of securely fastening the structure to the foundation to provide increased strength in earthquake and extreme weather.